Heat exchanger and system for warming and cooling a fluid circulating in a housing

ABSTRACT

A system for warming/cooling oil circulating within a power and torque transfer system of an automotive vehicle is disclosed. The system incorporates at least a first heat exchanger positioned between the inner wall of the outer housing and the outer surface of a gear forming part of the gear system enclosed within the housing, for instance a ring gear and/or pinion gear. The heat exchanger is generally formed as a single tubular member for conducting a first heat exchange fluid therethrough, the tubular member being curved to generally follow the curvature of the geometry of the inner wall of the housing and to fit within corresponding annular gaps. A second fluid channel is formed between the outer surface of the gear and the inner surface of the heat exchanger for bringing the oil into heat transfer relationship with the first heat exchanger fluid through rotation of the gear(s).

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of U.S. ProvisionalPatent Application No. 61/806,120 filed Mar. 28, 2013 under the titleHEAT EXCHANGER AND SYSTEM FOR WARMING AND COOLING A FLUID CIRCULATING INA HOUSING. The content of the above patent application is herebyexpressly incorporated by reference into the detailed description of thepresent application.

TECHNICAL FIELD

The invention relates to heat exchangers for warming and/or coolingfluids within an automobile power and torque transfer system. Inparticular, the invention relates to heat exchangers for mounting withina housing or casing for warming and/or cooling a fluid such as an oilcirculating within the housing.

BACKGROUND

It is well understood in the automobile industry that automobilesfunction most efficiently once all fluids are circulating within theautomobile systems at their optimum operating temperatures. Forinstance, heat exchangers for warming/cooling engine oil andtransmission oil are known and are often incorporated into automobilesystems in order to ensure that the fluids operate within the desiredtemperature range.

Axle oil and/or manual transmission oil are fluids within automobilesystems that benefit from warming and/or cooling in order to reduce thewarm-up time of the oil at start-up in order to bring the oil to optimaloperating temperature quickly thereby increasing the overall fueleconomy of the vehicle. Axle oil and/or manual transmission oil alsobenefit from cooling once the fluid has reached its desired operatingtemperature in order to protect not only the oil but to protect thecomponents through which the oil circulates.

Heat exchangers for warming/cooling oil that are located outside of thehousing of a power and torque transfer unit typically require an oilpump to flow the oil from within the housing to the externally locatedheat exchanger. Accordingly, heat exchangers mounted externally to thehousing of a power and torque transfer unit often require additionalcomponents resulting in a more complex and costly warming/cooling systemthat occupies more space within the automobile.

Heat exchangers can also be located inside the housing of a power andtorque transfer unit to allow for more direct contact between the heatexchanger and the oil circulating within the housing without requiringthe addition of a pump. However, conventional flat plate stacked heatexchangers are often difficult to package inside the housing of powerand torque transfer units due to the nature of the geometry of thehousing.

Differential housings and manual transmission housings often presentchallenges in terms of providing warming and/or cooling to the axle oilor transmission oil circulating within the respective housings due tothe complex geometry of the housing and the gear systems enclosed withinthem. Accordingly, there is a need for heat exchanger systems that canbe more easily packaged within housings of automobile power and torquetransfer components that have more complex geometry as a means forproviding warming and/or cooling functions to various automobile fluidsthat circulate within these types of housings in an effort to providecompact and cost-effective solutions with a view to improving overallefficiency of the vehicle.

SUMMARY OF THE PRESENT DISCLOSURE

In accordance with an exemplary embodiment of the present disclosurethere is provided a system for warming and/or cooling a fluidcirculating in a housing enclosing a gear system for a power and torquetransfer unit, the system comprising a heat exchanger positionedinterior the housing intermediate an outer surface of a gear within thegear system and an inner wall of the housing, the heat exchanger beingcurved about the axis of rotation of the gear, the heat exchangercomprising a tubular member having spaced apart walls defining a fluidpassageway therebetween for the flow of a first fluid through the heatexchanger; a primary heat transfer surface defined by one of the spacedapart walls of the tubular member; an inlet port and an outlet port influid communication with the fluid passageway for inletting anddischarging the first heat exchange fluid into the heat exchanger fromexterior the housing; and a second fluid passageway formed between theouter surface of the gear and the primary heat transfer surface for theflow of the fluid circulating within the housing therethrough; whereinthe fluid is brought into heat transfer relationship with the first heatexchange fluid flowing through the heat exchanger by means of rotationof the gear system.

In accordance with another exemplary embodiment of the presentdisclosure there is provided a heat exchanger for warming and/or coolinga fluid circulating in a housing of a power and torque transfer system,the heat exchanger comprising a tubular member having spaced apartwalls, the tubular member being non-planar and generally arcuate inshape; a first fluid passageway defined between the spaced apart walls;a primary heat transfer surface defined by an exterior surface of one ofthe spaced apart walls of the tubular member; an inlet opening in fluidcommunication with the first fluid passageway, the inlet opening formedon the spaced apart wall opposite to the primary heat transfer surface;an outlet opening in fluid communication with said first fluidpassageway, the outlet opening formed on the spaced apart wall oppositeto the primary heat transfer surface; and a second fluid passagewaydefined in part by the primary heat transfer surface.

In accordance with another exemplary embodiment of the presentdisclosure there is provided a differential unit for an automotivevehicle, comprising a gear system for transmitting torque and rotationto wheels of the automotive vehicle, the gear system comprising at leasta ring gear and a pinion gear, the ring gear and pinion gear arranged inmeshing relationship for rotational movement; a housing enclosing thegear system; a heat exchanger positioned interior the housingintermediate at least one of the ring gear or the pinion gear and aninner wall of the housing, the heat exchanger comprising a fluidpassageway for the flow of a first fluid through the heat exchanger; anda primary heat transfer surface arranged in spaced apart facingrelationship to an outer surface of the one of the ring gear and piniongear; at least one axle oil passageway defined between the primary heattransfer surface and the outer surface of the one of the ring gear andpinion gear for bringing axle oil into heat transfer relationship withthe first heat exchange fluid flowing through the heat exchanger;wherein the axle oil is delivered to the at least one axle oilpassageway through rotation of the pinion gear and the ring gear duringoperation of the gear system.

In accordance with another exemplary embodiment of the presentdisclosure there is provided a method for warming and/or cooling a fluidcirculating in a housing of a component of an automotive vehicleenclosing a gear system, the method comprising the steps of providing atleast a first heat exchanger in an annular gap formed between an outersurface of a gear in the gear system and an inner wall of the housing,the at least one heat exchanger defining a first fluid passagewaybetween spaced apart walls and forming a second fluid passageway betweenthe outer surface of the gear and one of the walls of the at least oneheat exchanger; supplying a first heat exchange fluid to the first fluidpassageway of the at least one heat exchanger; bringing a second heatexchange fluid into heat transfer relationship with the first heatexchange fluid in the at least one heat exchanger in the second fluidpassageways through operation and/or rotation of the gear system withinthe housing; wherein the second heat exchange fluid is a fluidcirculating within the housing of the component of the automotivevehicle.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being made to the accompanyingdrawings forming part of a specification, wherein like referencecharacters designate corresponding parts.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present disclosure will now be described byway of example with reference to the accompanying drawings, in which:

FIG. 1 is a cross sectional diagrammatic view of a power and torquetransfer unit, such as a differential, incorporating a heat exchanger inaccordance with an example embodiment of the present disclosure;

FIG. 1A is a cross-sectional diagrammatic view of a power and torquetransfer unit incorporating a heat exchanger in accordance with anotherexample embodiment of the present disclosure;

FIG. 1B is a cross-sectional diagrammatic view of a power and torquetransfer unit incorporating two heat exchangers in accordance withanother example embodiment of the present disclosure;

FIG. 2 is a cross sectional schematic view of a portion of the power andtorque transfer unit shown in FIG. 1;

FIG. 2A is a cross sectional schematic view of a portion of the powerand torque transfer unit shown in FIG. 1;

FIG. 3 is a schematic representation of an example embodiment of a heatexchanger for incorporating into the system of any of FIGS. 1, 1A, 1B;

FIG. 4 is a schematic representation of variation of the heat exchangershown in FIG. 3;

FIG. 5 is a schematic representation of another variation of the heatexchanger shown in FIG. 3; and

FIG. 6 is a schematic representation of two exemplary flow paths throughthe heat exchanger of any one of FIGS. 3-5.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

It is to be understood that the invention may assume various alternativeorientations and step sequences, except where expressly specified to thecontrary. It is also to be understood that the specific devices andprocesses illustrated in the attached drawings and described in thefollowing specification are simply exemplary embodiments of theinventive concepts defined herein. Hence, specific dimensions,directions or other physical characteristics relating to the exemplaryembodiments disclosed are not to be considered as limiting.

Referring now to FIG. 1, there is shown a cross sectional view of apower and torque transfer unit 10 in the form of a differential from anautomotive vehicle according to an example embodiment of the presentdisclsoure. As is understood in the art, the automotive vehicle ispowered by an internal combustion engine, the power generated by theengine being transmitted to a transmission and then through a powertrain or drive train, and eventually on to the drive wheels of thevehicle. The engine is connected to a pinion shaft 12 (a part of whichis shown in FIG. 1) and the driving wheels are connected to two othershafts (not shown), the power from the engine being transmitted from thepinion shaft 12 to the drive wheels through power and torque transferunit 10.

In the subject embodiment, the power and torque transfer unit 10, ordifferential, has an outer casing or housing 14 that has a generallycircular geometry for housing a gear system for transmitting torque androtation from the pinion shaft 12 to the wheels of the automotivevehicle. The gear system comprises a pinion gear 16 mounted at an end ofthe drive shaft 12, the pinion gear 16 being arranged in meshing contactwith a corresponding ring gear 18. The pinion gear 16 rotates in a firstdirection, indicated generally by directional arrow 20, the rotation ofthe pinion gear 16 causing the ring gear 18 to rotate in a seconddirection, indicated generally by directional arrow 21, as a result ofthe meshing relationship between the pinion gear 16 and the ring gear18, with the axes of rotation the respective gears 16, 18 beinggenerally perpendicular to each other. Additional gears are incorporatedinto the gear system contained within the power and torque transfer unit10 in accordance with principles known in the art. However, the warmingand cooling system according to the present disclosure will be describedprimarily in relation to the pinion gear 16 and ring gear 18 housed, forinstance, within the housing of a differential.

As shown in the drawings, the inner surface or inner wall 24 of theouter housing 14 has a generally circular configuration. The ring gear18 is sized and shaped so as to generally correspond to the geometry ofthe inner wall 24. A first gap 26 is formed between the inner wall 24 ofthe housing 14 and the outermost edge of ring gear 18. A second gap 28(as shown schematically in FIG. 2A) is formed between the inner wall 24of the housing 14 and outer surface of the pinion gear 16, the secondgap 28 likely being larger that first gap 26. While the first gap 26 isshown in FIG. 1 as being generally annular in shape with the size of thefirst gap 26 being rather consistent about the perimeter of the ringgear 18, it will be understood that this is not necessarily the case.More specifically, it will be understood that the actual shape and sizeof the first gap 26 will depend on the specific geometry andconstruction of the differential housing 14 as the size of the first gap26 will correspond to the actual distance between the outer surface ofthe ring gear 18 and the inner wall 24 of the housing 14 which may varyabout the perimeter of the ring gear 18.

Oil, or any other suitable lubricating fluid, is circulated through thehousing 14 to ensure proper functioning of the gear system. The bottomor lower portion 29 of the housing 14 typically acts as an oil sump orreservoir within the housing 14 in which the oil collects. Accordingly,the gap 26 found at the lower portion 29 of the housing 29 may be largerthan the gap 26 found elsewhere between the ring gear 18 and the innerwall 24 of the outer housing 14 about the perimeter of the ring gear 18.This may be due to the formation of a pocket or recessed area (shownonly schematically in FIG. 2) within the housing 14.

As the pinion gear 16 and ring gear 18 rotate within the housing 14, theoil circulates through the first and second gaps 26, 28 and around thevarious other components of the gear system creating an oil flow withinthe housing 14, the speed of the oil flow within the housing 14 varyingdepending upon the speed of rotation of the gears and depending upon theviscosity of the oil. Accordingly, the speed of the oil flow within thehousing 14 will also vary depending upon the temperature of the oilwhich will change, for instance, from cold start conditions to normaloperating temperatures due to the changes in viscosity of the fluid. Itis important that the oil flow within the housing 14 is maintained toensure that all of the components housed within the power and torquetransfer unit 10, or differential, are properly lubricated to ensureproper functioning of the components. In particular, in the case of adifferential, it is important that the oil flow within the housing 14reaches the pinion shaft 12 and associated pinion bearings 13 in thepocket 15 formed about the pinion shaft 12 within the housing 14 toensure adequate lubrication of these components during operation of thevehicle. Accordingly, oil flow to pinion shaft pocket 15 should not behampered or obstructed. Oil flow around the ring gear 18 in the firstgap 26 between the outer surface of ring gear 18 and in the innersurface 24 of the outer housing 14 is also desirable. It will beunderstood that a similar oil flow is created through the second gap 28between the outer surface of the pinion gear 16 and the inner wall 24 ofthe outer housing 14, as shown for instance in FIG. 2A.

At start-up, fluids within the automobile system (for instance engineoil, transmission oil, axle oil, manual transmission oil, etc.) are notat optimal operating temperatures as the fluids have increased viscositydue to the reduced temperature of the fluids at start-up which adverselyaffects the efficiency of the various automobile systems. As thetemperature of the fluids increase, through operation of the automobile,the viscosity of the fluids is reduced and the fluids flow moreefficiently through the fluid lines and within the various components ofthe automobile systems resulting in more efficient overall operation ofthe automobile itself. Accordingly, the power and torque transfer unit10, in this case the differential, will operate more effectively oncethe oil circulating through the housing 14 is at its optimal operatingtemperature. As the temperature of the fluids within the automobilesystem increase through operation of the automobile, it is alsoimportant to ensure that the temperature of the fluids remain in theiroptimal temperature range since the fluid properties breakdown outsidetheir optimal temperature range which can result in damage to varioussystems and/or components of the automobile, for instance thedifferential, or manual transmission.

Therefore, in accordance with the exemplary embodiment of the presentdisclosure, a first heat exchanger 30 is mounted within the first gap 26within the housing 14 of the power and torque transfer unit 10 in thiscase a differential, for example, between the ring gear 18 and the innerwall 24 in order to provide for warming and cooling of the oilcirculating within the housing 14 as shown schematically in FIGS. 1 and2. The first heat exchanger 30 comprises a tubular member 32 enclosing afluid passageway 34 for the flow of a first heat exchange fluid (e.g.coolant) through the heat exchanger 30. The fluid passageway 34 is influid communication with respective inlet and outlet ports 35, 36 forinletting and discharging the first heat exchanger fluid to and from theheat exchanger 30. While the tubular member 32 may be formed as aunitary, elongated tubular structure, it may also be formed by a pair ofcorresponding mating plate pairs 38, 40 as shown schematically in FIGS.3-6. For instance, the mating plate pairs 38, 40 may be formed having araised central portion surrounded by a peripheral flange that define thefluid passageway therebetween when the plates are arranged in theirface-to-face mating relationship in accordance with principles known inthe art. A turbulizer or other heat transfer augmenting device, i.e.dimples, ribs or other surface enhancements (shown only schematically inFIG. 4), may be positioned or formed within fluid passageway 34depending upon the particular design and application of heat exchanger30.

As shown more specifically in FIGS. 3-6, the tubular member 32 formingheat exchanger 30 is generally rectangular in shape although curved soas to generally follow the curvature of the inner wall 24 of the housing14 as well as the curvature of the outer edge of the ring gear 18.Accordingly, the heat exchanger 30 may be somewhat of a “banana-shaped”heat exchanger. The heat exchanger 30, therefore, is arcuate instructure having a length 42 corresponding to a portion of the outercircumference of the ring gear 18 (or inner circumference of the innerwall 24 of the housing 14), a width 44 corresponding generally to aportion of the width of the housing 14 and a depth 46 corresponding to aportion of the annular gap 26 provided between the ring gear 18 and theinner wall 24 of the housing 14 to enable oil to flow intermediate theheat exchanger 30 and the ring gear 18.

The fluid passageway 34 extends along the length 42 of the tubularmember 32. Accordingly, it will be understood that the heat exchanger 30is curved about an axis that is generally perpendicular to the directionof fluid flow in the passageway 34. Fluid passageway 34 can be designedas a single pass fluid flow passage way (e.g. I-flow) or as a two passfluid flow passageway (e.g. U-flow) as shown schematically in FIG. 6 inaccordance with principles known in the art. The inlet and outlet ports35, 36 are located on the back or outer surface 48 of the tubular member32 in communication with corresponding inlet/outlet fittings that extendthrough corresponding openings (not shown) formed in the wall of thehousing 14 for directing the first heat exchanger fluid into and out offluid passageway 34. Accordingly, when the heat exchanger 30 is designedas a single pass or I-flow heat exchanger, the inlet and outlet ports35, 36 are located at opposed ends of the heat exchanger 30. When theheat exchanger 30 is designed as a two pass or U-flow heat exchanger,the inlet and outlet ports 35, 36 are located adjacent to each other atone end of the heat exchanger 30. Accordingly, whether a single ortwo-pass heat exchanger 30 is used may depend on the desired location ofthe inlet/outlet fittings and/or the corresponding openings formed inthe housing 14.

The front or inside surface 50 of the tubular member 32 is generally acontinuous surface for transmitting heat to or from the first heatexchange fluid flowing through the tubular member 32 to or from the oilcirculating in the differential housing in the annular space or fluidchannel 53 formed between the ring gear 18 and the front or innersurface 50 of the heat exchanger 30. Accordingly, the oil circulating inthe fluid channel 53 between the ring gear 18 and the front or innersurface 50 of the heat exchanger 30 acts as a second heat exchange fluidthat is brought into heat transfer relationship with the first heatexchange fluid flowing through the heat exchanger 30. The front or innersurface 50 of the heat exchanger 30 is the primary heat transfer surfaceof the heat exchanger 30 and may be formed as a plain surface as shownin FIG. 3 or may be formed with protrusions 52 or other forms of surfaceenhancements (e.g. dimples, ribs, etc.) as shown schematically in FIG. 4for increasing heat transfer performance of the heat exchanger 30. Inother embodiments, a separate heat transfer surface 55 in the form of alow density fin or turbulizer may be mounted or fixed to the front orinner surface 50 of the heat exchanger 30, as shown schematically inFIG. 5, for increasing heat transfer performance of the heat exchanger30.

In some exemplary embodiments, the heat exchanger 30 is arranged andstrategically positioned within the first gap 26 to prevent oil fromactively flowing in the annular space 57 formed between the back orouter surface 48 of the heat exchanger 30 and the inner wall 24 of thehousing 14 so that there is little to no heat transfer on the outersurface 48 of the heat exchanger 30. In such instances, the annularspace 57 is minimized to effectively prevent active oil flow across theouter surface 48 of the heat exchanger 48 resulting in a thermalinsulation effect in the region of the annular space 57 that spans aportion of the housing 14 since any oil circulating within the housingthat has been warmed by heat exchanger 30 does not lose its heat to theouter housing 14. The annular space 57 can also serve as a supportingfixture and may also provide for vibration attenuation. In otherexemplary embodiments, however, the annular space 57 may serve as afluid channel for the flow of oil over the outer surface 48 of the heatexchanger 30 for heat transfer between the oil flowing in annular space57 and the first heat exchange fluid flowing through the heat exchanger30, especially in embodiments where the first gap 26 is large enough toallow for an annular space 57 between the inner surface of the outerhousing and the outer surface of the heat exchanger. Accordingly, inembodiments where oil does flow in the annular gap 57, it will beunderstood that both the inner and outer surfaces 50, 48 of the heatexchanger 30 serve as heat transfer surfaces.

In operation, the rotation of the pinion gear 16 and ring gear 18 causesthe oil from the sump or reservoir at the lower portion 29 of thehousing 14 to circulate within the housing 14 around the ring gear 18.As the oil flows over the upper portion of the ring gear 18 the oiltends to separate with a portion of the flow continuing in the directionof rotation of the ring gear 18, while another portion tends to flow inthe opposite direction, driven by gravity, back towards the sump orreservoir 29. The oil flow over the ring gear 18 is shown schematicallyin FIG. 2. The exact location of the separation in the oil flow from thesurface of the ring gear 18 depends on the ring gear speed as well asthe viscosity of the oil (or fluid) flowing over the gear and,therefore, will be different for different speeds of rotation and willalso depend on the temperature of the oil (or fluid) at variousoperating conditions. The heat exchanger 30, therefore, is sized andpositioned within the housing 14 to ensure that a maximum amount of oilflow passes through the fluid channel 53 to ensure optimal heat transferoccurs between the oil and the first fluid flowing through the heatexchanger 30. The positioning of heat exchanger 30 within first gap 26also does not adversely affect the oil flow within the housing 14 fromreaching the pinion shaft pocket 15.

A similar oil flow pattern occurs over the exterior of the pinion gear16 in the second gap 28 (shown in FIG. 2A) formed between the piniongear 16 and the inner wall 24 of the housing 14 with oil flow beingswept over the outer surface of the pinion gear 16 and being returned tothe sump or reservoir 29 while some flow separates and flows in anopposite direction, driven by gravity, towards the sump 29.

In instances where the geometry of the housing 14 or the componentshoused within the outer housing 14 is not conducive to having heatexchanger 30 positioned within the first gap 26 a second heat exchanger60 may be provided in the second gap 28 found between the outer surfaceof the pinion gear 16 and the inner wall 24 of the housing 14, as shownin FIG. 2A, as an alternative to the first heat exchanger 30 as shown inFIG. 1A. The second heat exchanger 60 generally has the same form as thefirst heat exchanger 30 described above and shown in FIGS. 3-6.Accordingly, heat exchanger 60 is generally rectangular in shape and, inthis instance, is curved so as to generally follow the curvature of theinner wall 24 of an upper portion of the housing 14 as well as thecurvature of the pinion gear 16 and, may, therefore, also be somewhat ofa “banana-shaped” heat exchanger. Therefore, the exact curvature of thefirst and second heat exchangers 30, 60 will be different given that thediameter of the pinion gear 16 is generally much smaller than thediameter of the ring gear 18.

It will also be noted that the second heat exchanger 60 is generallypositioned or oriented perpendicular to the general placement of thefirst heat exchanger 30. Therefore, whether the first or second heatexchanger 30, 60 is used, the first and second heat exchangers 30, 60are generally curved about the axis of rotation of the correspondinggear (i.e. the ring gear 18 or the pinion gear 16). Therefore, the fluidpassageway 34 in the second heat exchanger 60 will be oriented such thatthe flow direction within the fluid passageway 34 is generallyperpendicular to the flow direction associated with the fluid passageway34 in the first heat exchanger 30, when the first heat exchanger 30 isused. Accordingly, for both the first heat exchanger 30 and the secondheat exchanger, the tubular member 32 forming the heat exchanger 30, 60is curved about an axis that is generally perpendicular to the directionof fluid flow within the corresponding fluid passageway 34.

As with the example embodiment incorporating the first heat exchanger30, by positioning the second heat exchanger 60 over pinion gear 16, asecond fluid channel or passageway 54 is formed between the outersurface of the pinion gear 16 and the inner surface 50 of the secondheat exchanger 60 shown schematically in FIG. 2A. As the oil circulateswithin the housing 14 during operation of the vehicle, the oil will flowthrough the passageway 54 formed between the pinion gear 16 and thesecond heat exchanger 60 thereby bringing the oil into heat transferrelationship with the first heat exchanger fluid flowing through thesecond heat exchanger 60. By positioning heat exchanger 60 over thepinion gear 16 within the oil flow that is created within the mainhousing 14 during operation of the automobile, oil flow to the pinionshaft pocket 15 to provide lubrication to the pinion shaft 12 and pinionshaft bearings 13 is not adversely affected. Accordingly, warming and/orcooling of the oil can occur by means of strategic positioning of thefirst or second heat exchanger 30, 60 within the housing 14 withoutadversely affecting the operation of the power and torque transfer unit10.

As with the first heat exchanger 30, the second heat exchanger 60 can bedesigned with a single pass (i.e. I-flow) fluid passageway 34 or with atwo pass fluid flow passageway (i.e. U-flow) as shown schematically inFIG. 6 in accordance with principles known in the art. Once again, theinlet and outlet ports 35, 36 are located on the back or outer surface48 of the tubular member 32 forming the second heat exchanger 60 and arein communication with corresponding inlet/outlet fittings that extendthrough corresponding openings (not shown) formed in the wall of thehousing 14 for directing a first heat exchange fluid into and out offluid passageway 34 of the second heat exchanger. Therefore, whether thefirst or second heat exchanger 30, 60 is used, the first or second heatexchanger 30, 60 is in fluid communication with a coolant circuit withinthe overall automobile system. Depending upon the particular design ofthe warming and cooling system for the housing 14, the first or secondheat exchanger 30, 60 may be provided with the same first heat exchangefluid or with different first heat exchange fluids.

During operation of the automobile when the axle oil has reached itsoptimal operating temperatures, the rotation of the pinion gear 16 andring gear 18 causes the “hot” oil to flow within the fluid channels 53,54 formed by the annular gaps created between the outer surfaces of thering gear 18 or pinion gear 16, respectively and the corresponding innersurface 50 of the first or second heat exchanger 30, 60 depending onwhether a first or second heat exchanger 30, 60 is used. As the firstheat exchange fluid (i.e. coolant) flows in and out of the first orsecond heat exchanger 30, 60 that is strategically arranged in relationto the ring gear 18 or the pinion gear 16, heat is transferred from theoil circulating through the housing 14 to the first heat exchange fluidflowing through either the first and second heat exchanger 30, 60 whichultimately conducts the heat outside the housing 14 providing for rathercomplete cooling of the oil within the housing 14.

Conversely, at start-up conditions when the oil or fluid is cold and hasincreased viscosity due to the reduced temperature, as the first heatexchange fluid flows in and out of either the first or second heatexchanger 30, 60, heat can instead be transferred from the first heatexchange fluid to the oil circulating within the housing 14 in order toaide in bringing the oil or fluid, whether it be differential axle oilor manual transmission oil, up to its desired operating temperature.

In some instances, in order to provide for more complete warming and/orcooling of the oil circulating within the housing 14 of the power andtorque transfer unit 10, both the first and second heat exchanger 30, 60may be strategically positioned within the housing 14 in relation to thering gear 18 and the pinion gear 16 as in the above-describedembodiments. Therefore, warming and/or cooling by means of heatexchangers 30, 60 occurs in proximity to both the ring gear 18 andpinion gear 16. In such instances, depending upon the particular designof the warming and cooling system for the housing 14 of the power andtorque transfer unit 10, the first and second heat exchanger 30, 60 maybe provided with the same first heat exchange fluid or with differentfirst heat exchange fluids.

By assisting with both the cooling and/or warming of the oil circulatingwithin the power and torque transfer unit 10, such as a differential,the strategic arrangement of the first and/or second heat exchangers 30,60 within the housing in relation to the ring gear 18 and/or pinion gear16 allows the entire gear system housed within the casing 14 to operateproperly and efficiently thereby assuring long term reliability for thepower and torque transfer unit 10 which contributes to the overallperformance of the automobile.

While the above-described exemplary embodiment has been described makingreference to first and second heat exchangers 30, 60 with the first heatexchanger being positioned in relation to ring gear 18 and the secondheat exchanger being positioned in relation to pinion gear 16, it willbe understood that these terms have been used for ease of reference andthat, instead, a first heat exchanger could be positioned in relation tothe pinion gear 16 and a second heat exchanger positioned in relation tothe ring gear 18 or that only one of the first heat exchanger 30 andsecond heat exchanger 60 may be provided. More specifically, it will beunderstood that while the above-described exemplary embodiment has beendescribed as generally incorporating a first heat exchanger 30 or asecond heat exchanger 60, it Is contemplated within the scope of thepresent disclosure that the system may include either a first heatexchanger or a second heat exchanger arranged in relation to either thering gear 18 (as shown in FIG. 1) or in other embodiments in relation tothe pinion gear 16 (as shown in FIG. 1A) or that the system may includeboth a first heat exchanger and a second heat exchanger.

Furthermore, while the above-described exemplary embodiments has beendescribed primarily in relation to a power and torque transfer system orunit 10 of an automotive vehicle, such as a differential, it will beunderstood that the heat exchanger(s) and system according to thepresent disclosure can be modified for different applications within theautomotive vehicle, such as the manual transmission. More specifically,the manual transmission also comprises an outer housing 14 enclosing orencasing a gear system. During operation of the vehicle, transmissionoil circulates within the housing. While cooling of the transmission oilcirculating within the housing 14 may be advantageous in certainapplications, operation of the manual transmission would benefit fromwarming of the transmission oil circulating within the housing incertain situations in order to assist with bringing the transmission oilto its optimal operating temperature especially at cold-startconditions. Therefore, in order to provide for warming (and/or cooling)of the transmission oil in a manual transmission a first and/or secondheat exchanger 30, 60 can be arranged within the manual transmissionhousing intermediate the inner wall 24 of the housing 14 and the outersurface of corresponding gear forming part of the gear system enclosedtherein. The heat exchanger 30, 60 arranged within the manualtransmission housing will have a similar configuration as the heatexchanger 30, 60 described above and will function in a similar mannerin that a first heat exchange fluid flowing through the heatexchanger(s) will transfer heat to (or from) the transmission oil thatis brought into heat transfer relationship with the primary heattransfer surface of the heat exchanger by means of rotation of the gearswithin the gear system which causes the transmission oil to circulateand/or splash within the housing. Accordingly, similar arrangements asthose described above in connection with the power and torque transferunit 10 can be applied to differential systems, manual transmissionand/or other systems within an automotive vehicle involving an outerhousing enclosing a gear system with a fluid circulating within thehousing.

Therefore, while various exemplary embodiments have been described andshown in the drawings, it will be understood that certain adaptationsand modifications of the described exemplary embodiments can be made asconstrued within the scope of the present disclosure. Therefore, theabove discussed embodiments are considered to be illustrative and notrestrictive.

What is claimed is:
 1. A heat exchanger for warming or cooling a fluidcirculating in a housing of a power and torque transfer system, the heatexchanger comprising: a tubular member having spaced apart walls, thetubular member being non-planar and generally arcuate in shape; a firstfluid passageway defined between said spaced apart walls; a primary heattransfer surface defined by an exterior surface of one of said spacedapart walls of said tubular member; an inlet opening in fluidcommunication with said first fluid passageway, the inlet opening formedon the spaced apart wall opposite to said primary heat transfer surface;an outlet opening in fluid communication with said first fluidpassageway, the outlet opening formed on the spaced apart wall oppositeto said primary heat transfer surface; and a second fluid passagewaydefined in part by said primary heat transfer surface.
 2. The heatexchanger as claimed in claim 1, wherein in said tubular membercomprises a pair of mating non-planar generally arcuate plates, saidtubular member being curved about an axis generally perpendicular to thelongitudinal axis of said first fluid passageway.
 3. The heat exchangeras claimed in claim 1, wherein said inlet opening and said outletopening are arranged at opposed ends of said tubular member.
 4. The heatexchanger as claimed in claim 1, further comprising: a turbulizerpositioned in said first fluid passageway; and a heat transferaugmenting device mounted on said primary heat transfer surface whereinsaid heat transfer augmenting device is a low density turbulizer or fin.5. A differential unit for an automotive vehicle, comprising: a gearsystem for transmitting torque and rotation to wheels of the automotivevehicle, the gear system comprising at least a ring gear and a piniongear, the ring gear and pinion gear arranged in meshing relationship forrotational movement; a housing enclosing said gear system; a heatexchanger positioned interior the housing intermediate one of the ringgear or the pinion gear and an inner wall of the housing, the heatexchanger comprising: a fluid passageway for the flow of a first fluidthrough the heat exchanger; and a primary heat transfer surface arrangedin spaced apart facing relationship to an outer surface of said one ofthe ring gear and pinion gear; at least one axle oil passageway definedbetween said primary heat transfer surface and said outer surface ofsaid one of the ring gear and pinion gear for bringing axle oil intoheat transfer relationship with the first heat exchange fluid flowingthrough said heat exchanger; wherein said axle oil is delivered to saidat least one axle oil passageway through rotation of said pinion gearand said ring gear during operation of said gear system.
 6. Thedifferential unit as claimed in claim 5, wherein: said heat exchanger isa first heat exchanger arranged intermediate said ring gear and saidinner wall of said housing; and a second heat exchanger arrangedintermediate said pinion gear and said inner wall of said housing;wherein the first heat exchanger is curved about the axis of rotation ofthe ring gear and wherein the second heat exchanger is curved about theaxis of rotation of the pinion gear.
 7. The differential unit as claimedin claim 5, wherein said housing comprises a reservoir formed in a lowerportion of said housing in relation to said ring gear for collectingaxle oil.
 8. The differential unit as claimed in claim 5, wherein saidpinion gear is mounted on a pinion shaft for rotation within saidhousing, said housing comprising a pinion shaft pocket formed in innerwall of said housing about said pinion shaft for the flow of axle oilaround the pinion shaft proximal the pinion gear mounting.
 9. A methodfor warming or cooling a fluid circulating in a housing of a componentof an automotive vehicle enclosing a gear system, the method comprisingthe steps of: providing at least a first heat exchanger in an annulargap formed between an outer surface of a gear in said gear system and aninner wall of the housing, the at least one heat exchanger defining afirst fluid passageway between spaced apart walls and forming a secondfluid passageway between the outer surface of the gear and one of saidwalls of said at least one heat exchanger; supplying a first heatexchange fluid to said first fluid passageway of said at least one heatexchanger; bringing a second heat exchange fluid into heat transferrelationship with said first heat exchange fluid in said at least oneheat exchanger in said second fluid passageways through rotation of saidgear system within said housing; wherein said second heat exchange fluidis a fluid circulating within the housing of the component of theautomotive vehicle.
 10. The method as claimed in claim 9, the gearsystem comprising a ring gear and a pinion gear in meshing relationshipfor rotation within the housing, wherein the first heat exchanger isarranged between the ring gear and the inner wall of the housing. 11.The method of claim 9, the gear system comprising a ring gear and apinion gear in meshing relationship for rotation within the housing,wherein the first heat exchanger is arranged between the pinion gear andthe inner wall of the housing.
 12. The method of claim 9, wherein thecomponent is a differential and the second heat exchange fluid is axleoil.
 13. The method of claim 9 wherein the component is a manualtransmission and the second heat exchange fluid is transmission oil. 14.The method as claimed in claim 9, the gear system comprising a ring gearand a pinion gear in meshing relationship for rotation within thehousing, wherein the first heat exchanger is arranged in relation to oneof the ring gear and pinion gear, the method further comprising the stepof: providing a second heat exchanger in a gap formed between the otherof the ring gear or pinion gear and the inner wall of the housing, thesecond heat exchanger being oriented generally perpendicular to thefirst heat exchanger, the second heat exchanger defining a first fluidpassageway between the pinion gear and one of said walls of said secondheat exchanger; supplying said first heat exchange fluid to said firstfluid passageway of said second heat exchanger; and bringing said secondheat exchanger fluid into heat transfer relationship with said firstfluid in said second heat exchanger in said second fluid passagewaythrough rotation of said pinion gear and said ring gear.